BABIES22_093_LH.JPG A San Mateo woman,Luz Marie Marmolejo, 39 years old, gave birth on Monday to naturally conceived quadruplets. Born on Monday at Roni is now 2 1/2 pounds. He is one of the identical twins. Photographed by Liz Hafalia on 9/21/05 in Palo Alto, California. SFC Creditted to the San Francisco Chronicle/Liz Hafalia

BABIES22_120_LH.JPG A San Mateo woman,Luz Marie Marmolejo, 39 years old, gave birth on Monday to naturally conceived quadruplets. She is at a press conference at Lucille Packard Children's Hospital with her nine year old son, Fernando Marmolejo, and the father Yehonatan Tzairi (cq). Photographed by Liz Hafalia on 9/21/05 in Palo Alto, California. SFC Creditted to the San Francisco Chronicle/Liz Hafalia

In what doctors Wednesday described as a 1-in-a-million event, a San Mateo woman gave birth to quadruplets this week without the use of fertility drugs -- and two of the babies are identical twins.

"My mind is still trying to process all this," said Luz Maria Marmolejo, 39, who delivered the three boys and one girl by cesarean section Monday morning. "I was so excited to see them."

The babies were delivered at 27 weeks gestation, weighing between 2.2 and 2.6 pounds each. To help them breathe, they are on ventilators at Lucile Salter Packard Children's Hospital at Stanford, where they are being watched closely by doctors and nurses.

"They do have some infection issues, but so far they look good," said Dr. Ashima Madan, a neonatologist at Packard and an associate professor of pediatrics at Stanford School of Medicine. "I would say they are actually doing quite well," considering how early they were born.

Marmolejo and the babies' father, Yehonatan Tzairi, learned they were expecting quadruplets eight weeks into the pregnancy.

"I was in shock," Tzairi said.

The couple, who met while working at a South San Francisco moving company, relocated from a two-bedroom apartment in Millbrae to a four-bedroom home in San Mateo to get ready for the arrivals. They are counting on help from Marmolejo's large extended family and from her son Fernando, 9.

"I'll do everything to help," Fernando said. "Anything."

He already has a favorite: Kamilla, the lone girl, whom Marmolejo named after her maternal great-grandmother. A son, David, is named after her mother's older brother. The identical twins, Roni and Dror, are named after Tzairi's father and uncle, who are also twins.

Fertility treatments have increased the number of multiple births in the United States in recent years, but the odds of quadruplets conceived naturally -- as in Marmolejo's case -- are about 1 in 600,000 pregnancies, said Dr. James Smith, a perinatologist at Packard and clinical associate professor of obstetrics and gynecology at Stanford. It is even rarer for the outcome to include identical twins, he said.

"The chance of this happening is on the order of 1 in a million," said Smith, who cared for Marmolejo during her pregnancy. She spent the final two weeks on bed rest in the hospital as doctors tried to put off labor as long as possible to give the babies more time to develop.

Multiple births are more common in older mothers, Smith said. Luckily, they actually seem to do better than younger moms in the same situation.

"We're hoping for the best for these little babies," said Smith, who hopes they can leave the hospital around their original due date of Dec. 16. "But they're not out of the woods yet."